Processes for the production of methanol by reacting a gaseous mixture comprising hydrogen and carbon monoxide in the presence of a catalyst composition in a fluidized bed have been disclosed in the prior art.
A lecture reporting work by Y. Saito, M. Kuwa and O. Hashimoto during the 1987 Annual Meeting of the American Institute of Chemical Engineers, New York, Nov. 15-20, 1978, entitled "Development of a fluidized-bed methanol synthesis process" discloses a process using a reactor with the catalyst in a fluidized bed, cooled by means of a cooling jacket covering the surrounding wall of the bed. The temperature was adjusted by the temperature of the coolant (water being converted into high pressure steam). The temperature in the fluidized bed was essentially constant. This process requires high space velocities and causes a considerable drop in pressure over the reactor, the conversion per pass was about 16%. Unconverted carbon monoxide and hydrogen were recompressed and recycled through the reactor inlet.
A lecture reporting work by M.F.M. Post; S. T. Sie and J. M. Oelderik during the Chemeca'88 (Australia's Bicentennial International Conference for the Process Industries), Sydney Aug. 28-31, 1988, entitled "Synthesis of methanol in a fluidized bed of catalyst" discloses fluidized bed methanol synthesis at bench scale with conversions up to 60% at 8.1 MPa and 250.degree. C. (523.degree. K.) and good catalyst stability. For commercial scale operations the reported conversions were too low, however. The temperature in the fluidized bed in these experiments was essentially constant.
Also there is Chemical Week, 36 (Apr. 16, 1980) disclosing a process known as Chem Systems' three-phase process in which an inert liquid was used to fluidize the heterogeneous catalyst and to remove the heat of reaction. Good conversions per pass are claimed. However, the inert liquid caused mass transport problems and affected the reaction rate adversely. Moreover the process requires separation of methanol from the entrained liquid. The temperature in the reaction mixture was essentially constant, especially because the liquid has good temperature equalizing properties.
Cheap methanol in very large quantities is a valuable product as a fuel and a starting material for further chemical processing. Therefore there is a need for an economically attractive industrial bulk manufacturing process, using cheap starting materials and operating under attractive economical, environmental and safe conditions, i.e. using rather simple equipment and resulting in a significant reduction of the methanol cost price. Therefore considerable research and development efforts have been made for a further improved methanol manufacturing process.
The formation of methanol from hydrogen and carbon monoxide is a strongly exothermic equilibrium reaction so that relatively high operating pressures and temperatures are required for reasonable reaction rates, but under such reaction conditions the attainable conversion is strongly limited by the thermodynamic equilibrium. Finding a satisfactory compromise as to the reaction conditions between reaction rate and conversion percentage is therefore difficult. Effective control of the reaction temperature across the catalyst bed provide to be especially important.
An object of the present invention is the development of an industrial process for methanol manufacture with satisfactory conversion percentages in relatively simple equipment.